Search Results (61)

Additive manufacturing via LCD vat photopolymerisation enables direct bonding of photopolymer to textile substrates, but optimal processing parameters remain unclear. A 3 × 3 factorial design investigated the effects of layer thickness (0.01, 0.025, 0.05 mm) and UV exposure time (40, 80, 120 s) on the single-lap shear strength of woven fabric-photopolymer joints (65% polyester/35% cotton) using a novel pause-and-bond methodology, following the EN ISO 4587:2003 standard. Five replicate specimens per condition yielded 45 samples for mechanical testing. All specimens (45/45) exhibited adherend-limited failure within the textile substrate rather than at the polymer-textile interface, yielding consistent shear strengths of 1.38 ± 0.04 MPa (range: 1.30–1.45 MPa). Two-way ANOVA revealed no significant parametric effects (p > 0.05), indicating that interfacial bond strength consistently exceeded textile cohesive strength across all parameter combinations. The minimum resource-efficient condition (0.01 mm/40 s) achieves equivalent performance to higher-parameter combinations, enabling substantial process optimisation for textile-integrated photopolymer sandwich structures while reducing material and processing time requirements. Full article

Background: Digital light processing (DLP) 3D printing has emerged as a rapid alternative to labour-intensive micro-moulding for producing microneedle (MN) arrays, yet its use in biodegradable, dissolving MNs has been limited by proprietary, non-degradable resins. Methods: The current study proposed an innovative, biocompatible PEGDA–vinyl-pyrrolidone photo-resin with lithium phenyl(2,4,6-trimethylbenzoyl) phosphinate initiator, which systematically optimises its rheology and photo-reactivity for DLP printing. Resin formulations were evaluated through viscosity profiling, cure kinetics, FTIR, and ¹H NMR, and MN arrays were printed using a desktop DLP platform and characterised by optical microscopy, mechanical testing, thermal analysis, and dissolution studies. Results: A 40% PEGDA up-to 100% VP blend with 0.4% initiator was identified as providing rapid photopolymerisation, low shrinkage and complete vinyl conversion. Using a desktop DLP platform, 6 × 6 MN patches were printed in a single step without moulds and analysed by optical and scanning electron microscopy. The printed MNs reproduced CAD dimensions with <3% deviation, achieving a height of 1.40 ± 0.02 mm and a base thickness of 1.00 ± 0.01 mm, and showed a tip radius consistent with sharp penetration. Compression testing measured an array force of 32 N, corresponding to ~0.9 N per needle, exceeding the 0.2 N threshold for skin insertion. FTIR and ¹H NMR confirmed near-quantitative crosslinking, thermogravimetric and differential scanning calorimetry indicated stability at ambient conditions, and dissolution studies showed complete needle dissolution. Conclusions: An optimised PEGDA/VP resin yields geometrically precise, mechanically robust dissolving MNs in a single step, addressing the limitations of micro-moulding and paving the way for customisable, on-demand transdermal delivery of active molecules and biologics. Full article

The performance of dental composites is strongly dependent on the type and content of ceramic fillers incorporated into the resin matrix. In this study, the effect of nanosilica (NS) fillers on the curing kinetics, physicochemical, thermal, and mechanical properties of Bis-GMA/TEGDMA-based dental composites was systematically investigated. A series of nanocomposites containing various weight fractions of NS was prepared and evaluated. The photocuring behaviour was analysed using differential scanning calorimetry (DSC), enabling the determination of polymerisation rate coefficients (propagation k_p and bimolecular termination k_t^b) and double bond conversion. The presence of nanosilica was found to influence chain mobility, as evidenced by changes in glass transition temperature (T_g). Rheological measurements provided insight into viscosity changes induced by NS incorporation, while mechanical tests confirmed reinforcement effects. A moderate but statistically significant correlation was observed between the NS content and mechanical performance. The results obtained correlate the rheological, kinetic, thermal, and mechanical properties of multiple types of silica in a single resin system using a consistent methodology. In addition, the results highlight the role of nanosilica in the regulation of the curing dynamics and the increase in the mechanical integrity of methacrylate-based dental composites, representing a promising strategy for the development of next-generation restorative materials. Full article

Three-dimensional printing is growing rapidly in applied dentistry. To print faster, increase workflow, and minimise resin consumption, it is important to use the right printer and correct printing orientation. This report aims to analyse whether different printing orientations and types of printing materials could affect the flexural strength of a series of photopolymerisable resin samples. Seven different dental light-curing resins (Keyguide, C&B, Ivory, Vertysguide, Bite, Tera, and Nextdent Cast) and a single modern digital light processing (DLP) 3D printer (Moon Night) were used for this purpose. Different printing orientations (0°, 45°, and 90°) were evaluated. The resin specimens were designed using 3D Builder 20.0.4.0, MeshMixer 3.5.0 and Chitubox software 2.0.8. A total of 15 specimens (five for each orientation evaluated) in the shape of a rectangular parallelepiped with dimensions of 2 mm × 2 mm × 25 mm were produced for each of the seven selected resin materials with the Moon Night printer. After printing and post-processing (MoonWash 2 and MoonLight 2), each resin specimen was subjected to a mechanical test with a universal testing machine. After breaking the specimen, the flexural strength values were recorded using Bluehill computer software (Instron Corporation, Canton, MA, USA). According to the obtained results, the build angle does not affect the flexural strength of the printed products, whereas the difference occurs due to the different printing materials used. Full article

UV-cured methacrylated chitosan (MCHIT) hydrogels were achieved in the presence of silanised tellurium-doped silica bioactive glass (BG-Te-Sil) to produce an antimicrobial and osteoconductive scaffold for tissue engineering applications. Methacrylation of chitosan enabled efficient crosslinking, and the curing process was evaluated by means of Fourier-transform infrared spectroscopy (FTIR) and photorheology analyses. Compressive testing on crosslinked hydrogels showed that the silanised, bioactive, doped glass increased the hydrogel’s elastic modulus by up to 200% compared to unreinforced controls. Antibacterial assays against Staphylococcus aureus ATCC 43300 revealed a significant (p < 0.05) reduction in bacterial metabolic activity for hydrogels containing 50 wt% of the Te-doped bioactive glass. In vitro cytocompatibility with human bone-marrow mesenchymal stem cells demonstrated sustained viability and uniform distribution at 72 h (live/dead staining, AlamarBlue). Under H₂O₂-induced oxidative stress, reinforced hydrogels downregulated pro-inflammatory genes (TNF-α, IFN-γ, IL-1β, and PGES-2). These results suggest that the presence of the silanised bioactive glass can significantly enhance mechanical stability, antibacterial properties, and anti-inflammatory responses without affecting cytocompatibility, making these hydrogels promising for tissue engineering applications. Full article

The paper presents the design, manufacturing, and evaluation of a 3D-printed pancreas phantom model used for preoperative surgical planning and surgical training. Several manufacturing and design alternatives have been explored, leading to the final solution, which consisted of a transparent 3D printed elastic shell of the pancreas, resulting in an empty volume that was filled with a custom hydrogel to ensure an anatomically realistic behaviour. Additionally, specific vascular structures were printed using elastic material and specific colours. The hollow shell of the pancreas and the vascular structures were manufactured using photopolymerisation technology. The hydrogel, which replicates the internal structure of the pancreas, was made from a custom proportion of gelatine, agar, and glycerol. The phantom model of the pancreas was assessed by the surgical team and tested using the PARA-SILSROB parallel robot designed for single-incision surgical procedures. Full article

Using 3D-printed (3DPd) polymers and their composites as shape memory materials in various smart engineering applications has raised the demand for such functionally graded sustainable materials. This study aims to investigate the viscoelastic, shape memory, and fracture toughness properties of the epoxy-based ultraviolet (UV)-curable resin. A UV-based DLP (Digital Light Processing) printer was employed for the 3D printing (3DPg) epoxy-based structures. The effect of the hydrothermal accelerated ageing on the various properties of the 3DPd components was examined. The viscoelastic performance in terms of glass transition temperature (T_g), storage modulus, and loss modulus was evaluated. The shape memory polymer (SMP) performance with respect to shape recovery and shape fixity (programming the shape) were calculated through dynamic mechanical thermal analysis (DMTA). DMTA is used to reveal the molecular mobility performance through three different regions, i.e., glass region, glass transition region, and rubbery region. The shape-changing region (within the glass transition region) between the T_g value from the loss modulus and the T_g value from the tan(δ) was analysed. The temperature memory behaviour was investigated for flat and circular 3DPd structures to achieve sequential deployment. The critical stress intensity factor values of the single-edge notch bending (SENB) specimens have been explored for different crack inclination angles to investigate mode I (opening) and mixed-mode I/III (opening and tearing) fracture toughness. This study can contribute to the development of highly complex shape memory 3DPd structures that can be reshaped several times with large deformation. Full article

Background: The widespread adoption of clear aligners in orthodontic practice has driven the development of biomechanical devices to improve treatment efficiency. The mechanical properties of these materials play a critical role in determining their clinical performance and efficacy. This study investigates the Young’s modulus of Clear-Blokker^® (Scheu Dental), a photopolymerisable resin used for the attachment of clear aligner, and evaluates its mechanical behaviour under different curing times (5 s and 10 s) and environmental conditions (dry storage and immersion in artificial saliva at 37 °C). Methods: Forty-eight cylindrical specimens were prepared and subjected to quasistatic compression tests after 14 days. A multi-factorial analysis of variance (ANOVA) at a significance level of 5% was performed to compare the variances. Results: The results showed that samples immersed in artificial saliva had significantly reduced Young’s moduli compared to samples stored in dry conditions (p = 0.0213), while no significant difference was observed between curing times. Conclusions: The results suggest that Clear-Blokker^® has mechanical properties comparable to those of clear aligner materials, making it suitable as a biomechanical aid for orthodontic treatment. However, further clinical studies are required to confirm its long-term efficacy in the oral environment. Full article

The efficiency of photopolymerisation significantly impacts achieving a high degree of conversion and, consequently, determines the success and strength of resin-based composite (RBC) restorations. The study aimed to measure the light irradiance of selected LED curing lamps, taking into account various exposure modes and the increased distance of the light source from the radiometer surface. The study material consisted of 21 LED polymerisation lamps of a single type (Woodpecker Medical Instrument Co., Guilin, China) with three exposure modes: standard, soft start, and pulse. During the measurement, the distance was increased from 0 mm to 8 mm, every 2 mm. Light irradiance measurements were made with a Bluephase Meter II photometer (Ivoclar Vivadent, Opfikon, Switzerland). Increasing the distance affected the soft mode the most, causing a significant drop in light irradiance on the photometer. Standard mode coped best with distance. Even at a distance of 0 mm, the soft start mode does not reach the power of the standard and pulse modes. The standard mode seems to be the most clinically effective, especially if it is planned to polymerise a material in a deep cavity. The soft start mode, as the least resistant to increasing distance, is recommended for use in front teeth or the cervical area. Full article

Poly (N-vinylcaprolactam) (PNVCL) and poly (N-isopropylacrylamide) (PNIPAm) are two popular negatively temperature-responsive hydrogels, due to their biocompatibility, softness, hydrophilicity, superabsorbency, viscoelasticity, and near-physiological lower critical solution temperature (LCST). These characteristics make them ideal for biomedical applications. When combined with other materials, hydrogel expansion induces the morphing of the assembly due to internal stress differences. Our recent developments in NVCL hydrogel, enhanced by nanoclay incorporation, have driven us to the creation of a bilayer structure to study its shapeshifting response across various temperatures. This study focused on the bending behaviour of bilayer samples composed of an active hydrogel layer and a passive non-swellable layer. Using photopolymerisation, circular discs and rectangular bilayer samples of varying sizes were fabricated. Homogeneous circular samples demonstrated that hydrogel density increased proportionally with temperature, with the swelling ratio exhibiting two distinct rates of change below and above its LCST. In bilayer samples, the volume of the passive layer influenced bending, and its optimal volume was identified. The investigation revealed that geometry affected the overall bending effect due to changes in the passive layer stiffness. Lastly, a temperature-responsive gripper capable of picking up objects several times its own weight was demonstrated, highlighting the potential of NVCL hydrogels as bioactuators for minimally invasive surgery. Full article

Additive manufacturing (AM) has revolutionised the manufacturing industry, offering versatile capabilities for creating complex geometries directly from a digital design. Among the various 3D printing methods for polymers, vat photopolymerisation combines photochemistry and 3D printing. Despite the fact that single-epoxy 3D printing has been explored, the fabrication of multi-material bioderived epoxy thermosets remains unexplored. This study introduces the feasibility and potential of multi-material 3D printing by means of a dual-vat Digital Light Processing (DLP) technology, focusing on bioderived epoxy resins such as ELO (epoxidized linseed oil) and DGEVA (vanillin alcohol diglycidyl ether). By integrating different materials with different mechanical properties into one sample, this approach enhances sustainability and offers versatility for different applications. Through experimental characterisation, including mechanical and thermal analysis, the study demonstrates the ability to produce structures composed of different materials with tailored mechanical properties and shapes that change on demand. The findings underscore the promising technology of dual-vat DLP technology applied to sustainable bioderived epoxy monomers, allowing sustainable material production and complex structure fabrication. Full article

Non-metallic additive manufacturing technology has seen a substantial improvement in the precision of the parts it produces. Its capability to achieve complex geometries and very small dimensions makes it suitable for integration into strategic industrial sectors, such as aeronautics and medicine. Among additive manufacturing technologies, resin development processes demonstrate enhanced precision when compared to other methods, like filament printing. This study conducts a comparative analysis between digital light processing (DLP) and liquid crystal display (LCD) photopolymerization processes to assess the performance of the technologies and how process parameters affect the accuracy of the resulting parts. The research evaluates the impact of the discretization process used during the digital model export, determining the optimal mesh size and then analyzing the geometric deviations that occur by altering various operating parameters of the process. Statistical methods will be employed to identify the most significant parameters in the manufacturing process. Among other aspects, the precision of manufacturing technologies regarding the movement axis has also been evaluated. Regarding the minimum size of the features that can be fabricated, DLP technology has surpassed LCD technology, successfully producing features as small as 200 µm, compared to 500 µm for LCD technology. Full article

Following the formulation development from a previous study utilising N-vinylcaprolactam (NVCL) and N-isopropylacrylamide (NIPAm) as monomers, poly(ethylene glycol) dimethacrylate (PEGDMA) as a chemical crosslinker, and Irgacure 2959 as photoinitiator, nanoclay (NC) is now incorporated into the selected formulation for enhanced mechanical performance and swelling ability. In this research, two types of NC, hydrophilic bentonite nanoclay (NCB) and surface-modified nanoclay (NCSM) of several percentages, were included in the formulation. The prepared mixtures were photopolymerised, and the fabricated gels were characterised through Fourier transform infrared spectroscopy (FTIR), cloud-point measurements, ultraviolet (UV) spectroscopy, pulsatile swelling, rheological analysis, and scanning electron microscopy (SEM). Furthermore, the effect of swelling temperature, NC types, and NC concentration on the hydrogels’ swelling ratio was studied through a full-factorial design of experiment (DOE). The successful photopolymerised NC-incorporated NVCL-NIPAm hydrogels retained the same lower critical solution temperature (LCST) as previously. Rheological analysis and SEM described the improved mechanical strength and polymer orientation of gels with any NCB percentage and low NCSM percentage. Finally, the temperature displayed the most significant effect on the hydrogels’ swelling ability, followed by the NC types and NC concentration. Introducing NC to hydrogels could potentially make them suitable for applications that require good mechanical performance. Full article

Additive and lithographic manufacturing technologies using photopolymerisation provide a powerful tool for fabricating multiscale structures, which is especially interesting for biomimetic scaffolds and biointerfaces. However, most resins are tailored to one particular fabrication technology, showing drawbacks for versatile use. Hence, we used a resin based on thiol-ene chemistry, leveraging its numerous advantages such as low oxygen inhibition, minimal shrinkage and high monomer conversion. The resin is tailored to applications in additive and lithographic technologies for future biofabrication where fast curing kinetics in the presence of oxygen are required, namely 3D inkjet printing, digital light processing and nanoimprint lithography. These technologies enable us to fabricate scaffolds over a span of six orders of magnitude with a maximum of 10 mm and a minimum of 150 nm in height, including bioinspired porous structures with controlled architecture, hole-patterned plates and micro/submicro patterned surfaces. Such versatile properties, combined with noncytotoxicity, degradability and the commercial availability of all the components render the resin as a prototyping material for tissue engineers. Full article

Background and objectives: Inflammatory bowel disease is a chronic condition with no cure. However, there are a range of treatment options. Pharmacological approaches are usually the first step in treatment, and they are effective for many patients; however, for some, side effects are evident, and effectiveness can reduce overtime. Research on advanced delivery systems, new drugs and the therapeutic benefits of nutraceuticals such as curcumin have been previously investigated with promising results for IBD treatment, although they present their own unique challenges including poor bioavailability. The poor bioavailability of hydrophobic agents including curcumin is partly attributed to poor solubility and inadequate concentrations at target tissues. Therefore, the aim of the present work was to develop a novel pH-sensitive drug and nutraceutical delivery system featuring microspheres embedded in a hydrogel. Methods: Polylactic acid–polyethylene glycol microspheres loaded with dexamethasone (0.8 wt%) and curcumin (0.8 wt%) were synthesised using an emulsion solvent evaporation method. pH-sensitive polyethylene glycol dimethacrylate-co-acrylic acid hydrogels (46.6% and 33.3%, respectively) were synthesised with water (20%) by UV-photopolymerisation. The dexamethasone and curcumin microspheres were embedded into the hydrogels. Hydrogels and microspheres were characterised separately to understand their properties. Results: The encapsulation efficiency of the dexamethasone and curcumin microspheres was promising with higher encapsulation efficiency achieved for the curcumin microspheres (29% and 92%, respectively). Swelling studies demonstrated the equilibrium water content (EWC), the ability of the hydrogel to uptake its surrounding solution, with differences observed in response to changes in pH. In pH 6.8, hydrogels took up more of the surrounding solution compared to pH 2.2 (EWC% after 24 h = 69% and 56%, respectively). Gel fraction studies showed that the efficiency of the network formed during photopolymerisation (96%). Discussion: This targeted drug and nutraceutical delivery system may have the potential to play a role for IBD treatment with the combined impact of the microspheres in the hydrogel to be established. Dexamethasone and curcumin were encapsulated into microspheres which aid their solubility. The hydrogel component may help achieve a targeted delivery system, owing to the changes observed in response to different pH levels, as would be observed along the gastrointestinal tract. Full article